Karol Borsuk (May 8, 1905, Warsaw - January 24, 1982, Warsaw) was a Polish mathematician. His main interest was topology. Borsuk introduced the theory of "absolute retracts" (ARs) and "absolute neighborhood retracts" (ANRs), and the cohomotopy groups, later called Borsuk-Spanier cohomotopy groups. He has constructed various beautiful examples of topological spaces, e.g. an acyclic, … Wikipedia
The definitive Wikipedia entry for Karol Borsuk. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Karol_Borsuk
